The study intends to explore postural aberrations in autistic children as compared to deaf-neurologically impaired, deaf normal, and normal hearing children. A specific posturographic technique called "tetra-ataxiametry" will be used. The latter measures the vertical pressures of each heel and toe part on four electronically sensitive plate forms. Some postures will be examined under the stress of optokinetic stimulation and during the execution of intentional pedal motor acts. The main objective measures of postural control obtained by this method are a) spectral analysis of sway, sensitive the dominance of labyrinthine- visual vs. proprioceptive feedback, and b) postural synchrony, which reflects the co-activation of ipsilateral and contralateral agonists are antagonists of the lower extremities. As two recent neuro-anatomical theories seek to roots of autism in dysfunctions of the vestibular system and the brain-stem on the one hand, and in disturbances located in the mesocortex, the striatum and the supplemental motor area on the other, i.e. in brain centers known to be intimately linked with postural control, it is assumed that the posturographic parameters described above might be sensitive to the specific CNS deficiencies linked with autistic behavior, according to these theories. The proposed study will also explore the eventual correlations between and the degree and pattern of postural aberrations in autistic children. Finally, findings of the study are expected to contribute to the formulation of a typology of autism, based on intragroup differences in postural control patterns and their interpretations as indicators of specific neuropathology on the one hand, and typical behavioral symptoms on the other. The populations of the target and comparison group (altogether 480 Ss) will be recruited from special and regular schools, as well as from psychiatric clinics in Israel and in Connecticut, U.S.